male parent vs pa

male parent and pa both are nouns.

Word	Noun	Adjective	Verb	Adverb
male parent	Yes	No	No	No
pa	Yes	No	No	No

As nouns, pa is a hyponym of male parent; that is, pa is a word with a more specific, narrower meaning than male parent:

Other hyponyms of male parent include dad, dada, daddy, papa, pappa, pop, father-in-law, old man, pater.

male parent (noun)	pa (noun)
a male parent (also used as a term of address to your father)	an informal term for a father; probably derived from baby talk